Photographic objective.



350-470 SR OR 745.550 1ml 7 #023 K 110145550. PATENTED DEG.1,1903.

W. ZSGHOKKE & F. URBAN.

PHOTOGRAPHIG OBJECTIVE;

I APPLICATION FILED mm. 14, 1903.

no MODEL.

" terior shape of the lenses. relative dispersions of the lenses, or, more NALTHER ZSCHOKKE Al'll- FRA NZ URBAN, OF STEGLITZ, NEAR BERLIN,

GERMANY, ASSIGNORS '1 o r NEAR BERLIN, GERMAN-Y1 FIRM OF C. P. GOERZ, OF FRIEDENAU,

SPECIFICATION forming part of Letters Patent No. 745,5 dated Dece 1903- Application filed February 14, 1903. Serial No. 143,446. No model.)

To all whom it may concern:

Be it known that we, WALTHER ZSCHOKKE and FRANZ URBAN, citizens of the German Empire, and residents of Steglitz, near Berbe seen from United States Patent No.635,472 to Goerz and von Hoegh. N owit has been found that all defects of the image produced, especially spherical and chromatic aberration and astigmatism, effectually can be eliminated in a two-lens system consisting of a biconvex lens and a biconcave lens if the biconvex crown glass lens has a refractive power equal to or lower than that of the biconcave flint-glass lens. This result can be obtained without materially altering the ex- Oonsequently the correctly spoken, of the kinds of glass from which the lenses are formed, may be the same as in the case of the objective forming the object of the said United States patent numbered 635,472, whereas the absolute amounts of dispersion obviously must be different.

A double objective in accordance with our invention is represented on the accompanying drawing.

L is the biconcave lens, and L the biconvex lens, of the two-lens system forming the object of the invention.

R R R R designate the several surfaces of the lenses and at the same time the radii of curvature of same.

The constructional elements of the new objective are given in the table below in millit 'tidttx lens leaving between them an airjective being two hundred and forty milliopening being about two-elevenths of the 0- The novel feature of the above-described States Patent No. 635,472, referred to, consists in the substitution of the barium crownglass of high refractive power (for the biconvex lens) by ordinary silicate crown-glassof lower refractive power. This modification is that barium crown-glass is very precious, and nevertheless its high price not free from bubbles and blisters, causing considerable loss of material in the manufacture of the lenses.

costs one-third of the price of the barium crown-glass and can easily be manufactured in clear and uniform quality, so that the loss of material is considerably diminished. More over, the silicate crown-glass is in a higher degree transparent, light, and permanent.

It is obvious that we may combine two objectives of the kind above described in order to obtain a double objective having certain advantages over the simple two-lens objective, as is well understood.

Having now particularly described and as certained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is- 1. A two-lens objective for photographic purposes consisting of a biconcave lens and refractive power and said biconvex lens havi'ng low refractive power.

meters, and the greatest effective area or 5 lin, in the Kingdom of Prussia and German cal length or distance.

Empire, have invented certain new and useful Improvements in Photographic Objec- Radius of curvature Len th tives, of which the following is a specification. the surface' g Our invention relates to an objective for no photographic purposes composed of a bicon- EE- (ml-mess 0f the lens cave lens and a biconvex lens, leaving be- R 184 11 -51 g l i knes i of thelayer tween them an air-space having the form of a Rs H2430 21 25 @fiffi 3 2 x 12, positive meniscus; and it consists in certain improvements hereinafter specified, and

I I5 pointed out in the claims. Hitherto it has been thought necessary in connection with i glass 9 has the followmg objectives of this kind to employ glass of low lea proper refractive 1power ior the manufacture ofhthe L: n 1.53296 n 1.56199 0-- F=O.0l094-.

. biconcave ens an to em 0 ass of hi rez'o fractive power for the bi dori vgx lens, a? may L012 C F=OOO87O 7o objective over the objective of the United of high practical value in view of the fact The silicate crown-glass,on the contrary, only ,1 space having the form of a positive menisone, said biconcave lens having high refrac- Signed this 27th day of January, 1903, at

4.; f V tive power and said biconvex lens having low Berlin.

refractive P WALTHER ZSOHOKKE. 2. An ob ective conslstingof two compound FRANZ URBAN.

systems, each composed of a biconcave lens a a and a biconvex lens, leaving between them Witnesses:

HENRY HASPER,

' an air-space having the form of a positive WOLDEMAR HAUPT.

iff 1o meniscus, said biconcave lens having high 

